1. Technical Field
The present invention relates to an electric tool switch.
2. Related Art
A trigger switch including a trigger pulled towards a grip of an electric tool is conventionally used as a switch having a speed adjustment function for the electric tool. The trigger switch is interposed between a battery and a motor, and adjusts the rotating speed of the motor by outputting a voltage of a current-flow ratio corresponding to the pulled amount of the trigger.
The trigger switch normally includes a variable resistor in which a slidably moving element that moves with the trigger slidably contacts a print resistor formed on a circuit substrate, and adjusts the output to the motor by changing the conduction time ratio of the switching element by changing the resistance value of the variable resistor according to the pulled amount of the trigger.
The trigger switch enabling the motor to be rotated in a reverse direction includes a switching switch for inverting a polarity of the output. Japanese Patent No. 3768400 describes an invention in which two circuits, in which the resistance value changes differently according to the pulled amount of the trigger, are arranged in parallel to cause the rotating speed of the motor with respect to the pulled amount of the trigger to differ at the time of forward rotation and at the time of reverse rotation of the motor, and only one of the circuits is connected by the switching switch for inverting the polarity of the output.
When using the electric tool that uses the trigger switch, the user sensuously grasps the pulled amount of the trigger, but subtle difference in the pulled amount is difficult to recognize and only a rough speed control can be carried out.
The task is sometimes interrupted when the tool is switched from one hand to the other or the hand is released from the work to operate the switching switch.